1. Field of the Invention
The present invention relates to a shaft-seal device for high-temperature fluid used in rotating machines (for example, a steam compressor, a compressor, a blower, a pump, or a stirrer that is used in a nuclear power generation system, among others) that deals with high-temperature fluid such as high-temperature steam and boiler water.
2. Description of the Related Art
In this type of shaft-seal device, as a sealing means, a mechanical seal is used, in which the sealing performance is provided by the relative rotation effect of the sealing end-faces that are the facing end-faces of a rotational sealing ring fixed to a rotary shaft, and a stationary sealing ring held to a seal case with an O-ring interposed so as to be movable in the axial direction. Normally, to prevent heat damage of the mechanical seal components, it is devised so that the components, such as the sealing ring, are cooled by setting up a water jacket or a flushing path in the seal case (for example, see Patent Documents 1-3).    [Patent Document 1] Japanese Patent Application Laid-Open (Kokai) No. 2001-349443    [Patent Document 2] WO 2008/132958    [Patent Document 3] WO 2008/142945
However, the reality is that the mechanical seal members, to which the high-temperature fluid that is the sealed fluid comes in contact directly, cannot be cooled sufficiently by the cooling means described above, causing various troubles. Such mechanical seals members include an O-ring used as a sealing ring serving as a secondary seal between the seal case and the stationary sealing ring, and an O-ring for the case, interposed between the seal case and the housings of the rotating apparatus installed to this seal case. For example, when high-temperature fluid comes in contact with an O-ring used as a sealing ring, there is a danger that the O-ring deteriorates even if it is constituted of a heat resistance material such as fluorocarbon resin, the secondary seal function and the suppleness of the stationary scaling ring deteriorate, and the mechanical seal function decreases and becomes lost.